diff --git a/STM32F1/cores/maple/wirish.h b/STM32F1/cores/maple/wirish.h
index fbee81f..d925df6 100644
--- a/STM32F1/cores/maple/wirish.h
+++ b/STM32F1/cores/maple/wirish.h
@@ -44,6 +44,7 @@
 
 #include <string.h>
 #include <WString.h>
+#include <avr/dtostrf.h>
 #include <avr/pgmspace.h>
 #include <avr/interrupt.h>